Abstract: The Bayinnuoergong granite pluton in the southeast of Alxa Block is located to the northwest of North China Craton and distrbuted in Yabula-Bayinnuoergong tectonic belt in the south of Huoershen-Chaganchulu tectonic belt, controlled generally by NEE-trending structure. It consists of medium to fine grained biotite granite and medium to coarse porphyritic biotite granite. Re-searchers have done some research on the ages of the Bayinnuoergong granite, which provides a favorable condition for analyzing and discussing whether the Bayinnuoergong intrusion formed in multiperiodic magmatic activities. TIMS U-Pb dating of zircons from the Bayinnuoergong medium to fine grained biotite granite and medium to coarse porphyritic biotite granite yielded two ages of 304.7± 2.8Ma and 289.0± 3.8Ma, respectively, indicating that the pluton should be the Late Carboniferous-Early Permain intrusion. Combined with the previous research in the study area, it is held that there are at least two magmatic activities in this area, which oc-curred in Late Carboniferous (304Ma) and Early Permian (289~272Ma).